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perf/core: Fix perf_mmap fail when CONFIG_PERF_USE_VMALLOC enabled

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This problem can be reproduced with CONFIG_PERF_USE_VMALLOC enabled on
both x86_64 and aarch64 arch when using sysdig -B(using ebpf)[1].
sysdig -B works fine after rebuilding the kernel with
CONFIG_PERF_USE_VMALLOC disabled.

I tracked it down to the if condition event->rb->nr_pages != nr_pages
in perf_mmap is true when CONFIG_PERF_USE_VMALLOC is enabled where
event->rb->nr_pages = 1 and nr_pages = 2048 resulting perf_mmap to
return -EINVAL. This is because when CONFIG_PERF_USE_VMALLOC is
enabled, rb->nr_pages is always equal to 1.

Arch with CONFIG_PERF_USE_VMALLOC enabled by default:
	arc/arm/csky/mips/sh/sparc/xtensa

Arch with CONFIG_PERF_USE_VMALLOC disabled by default:
	x86_64/aarch64/...

Fix this problem by using data_page_nr()

[1] https://github.com/draios/sysdig

Fixes: 906010b213 ("perf_event: Provide vmalloc() based mmap() backing")
Signed-off-by: Zhipeng Xie <xiezhipeng1@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220209145417.6495-1-xiezhipeng1@huawei.com
This commit is contained in:
Zhipeng Xie 2022-02-09 09:54:17 -05:00 committed by Peter Zijlstra
parent b2d229d4dd
commit 60490e7966
3 changed files with 6 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
kernel/events/core.c
View File

@ -6247,7 +6247,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
again:
mutex_lock(&event->mmap_mutex);
if (event->rb) {
if (event->rb->nr_pages != nr_pages) {
if (data_page_nr(event->rb) != nr_pages) {
ret = -EINVAL;
goto unlock;
}

5
kernel/events/internal.h
View File

@ -116,6 +116,11 @@ static inline int page_order(struct perf_buffer *rb)
}
#endif
static inline int data_page_nr(struct perf_buffer *rb)
{
return rb->nr_pages << page_order(rb);
}
static inline unsigned long perf_data_size(struct perf_buffer *rb)
{
return rb->nr_pages << (PAGE_SHIFT + page_order(rb));

5
kernel/events/ring_buffer.c
View File

@ -859,11 +859,6 @@ void rb_free(struct perf_buffer *rb)
}
#else
static int data_page_nr(struct perf_buffer *rb)
{
return rb->nr_pages << page_order(rb);
}
static struct page *
__perf_mmap_to_page(struct perf_buffer *rb, unsigned long pgoff)
{